When Maryland National Guard Capt. Cara Kupcho first enlisted in the military 18 years ago, she wanted to drive a Bradley Fighting Vehicle, a 30-ton, armor-busting tank.

"I like things that go boom," she explained Thursday. "I like tanks."

But as a woman, Kupcho was barred from joining any of the armored units that used the vehicles. She became a mechanic instead, able to maintain tanks, but prohibited from driving them into battle.

Outgoing Defense Secretary Leon Panetta announced plans Thursday to end the long-standing prohibition on servicewomen in direct combat roles, opening hundreds of thousands of jobs formerly limited to men.

"In our democracy, I believe it is the responsibility of every citizen to protect the nation," Panetta said. "And every citizen who can meet the qualifications of service should have that opportunity."

The decision to end the so-called combat exclusion policy followed the unanimous recommendation of the Joint Chiefs of Staff. Panetta directed the Army, Navy, Air Force and Marines to submit plans to implement the change by May 15.

The services have until January 2016 to declare exceptions for roles that they believe should remain off-limits to women — but it was unclear whether they would.

Army Gen. Martin Dempsey, the chairman of the Joint Chiefs, suggested that women would be allowed to compete for spots not only in armored, artillery and infantry units, but in such elite Special Operations organizations as the Army's Delta Force and the Navy's SEALs.

"I think we all believe that there will be women who can meet those standards," he said.

The decision comes after more than a decade of war in Iraq and Afghanistan, where female service members have increasingly been exposed to the fighting.

While women have been officially barred from units that engage in direct combat with the enemy, commanders have routinely tapped women to work alongside the men who staff those units.

Of the more than 280,000 women who have served in Afghanistan or Iraq since Sept. 11, 2001, more than 150 have been killed and nearly 1,000 wounded.

Army Staff Sgt. Jennifer Hunt, a Gaithersburg reservist, earned a Purple Heart in 2007 when her Humvee rolled over a roadside bomb in Baghdad.

Hunt, who also joined male soldiers on village raids in Afghanistan to search any females they found, is one of four U.S. servicewomen who sued Panetta last year to end the exclusion policy.

It was unclear whether that lawsuit or a similar one filed by two other servicewomen last year played a role in Panetta's decision.

The Pentagon had begun in recent years to expand opportunities for women.

Last year, the Army opened about 14,500 jobs previously off-limits to women, including intelligence and personnel officers and artillery and tank mechanics, and began recruiting female pilots and crew chiefs this month to fly Special Operations helicopters.

The Marine Corps allowed women to attend its grueling Infantry Officer Course and began assigning women to train in certain combat-related jobs with infantry, artillery, tank and other units for testing purposes.

But those were small steps compared with the announcement Thursday, which could open about 238,000 jobs, most of them in the Army and Marines, the "tip of the spear" of the U.S. military.

"It's a great opportunity for women," Maryland National Guard Sgt. Myoung Fisher said. "I'm glad to be working in an organization where there are no limits to what I can do."

Women make up 15 percent of the 1.4 million active-duty service members. Annette Deener, a retired brigadier general in the Maryland National Guard, said women have earned the opportunity to compete for combat jobs.

"Since 9/11, women have really proved themselves on the battlefield," said Deener, now chief of staff of the Maryland Military Department. "I think that influenced the decision."

Fifteen female members of the Maryland Guard have earned the Combat Action Badge in Iraq or Afghanistan. The badge is awarded to noninfantry soldiers who have actively engaged or been engaged by the enemy.

About 20 percent of the jobs in the 6,400-member Maryland National Guard are restricted to men, including infantry, cavalry and Special Forces specialties.

Deener, who joined the now-defunct Women's Army Corps in 1975, called the decision to open these jobs to females "great — as long as women can meet the same standards as men."

Panetta said the services would set clear, "gender-neutral" standards for all military occupations. It would be up to Congress to decide whether to require women to register for the Selective Service on turning 18.

While Panetta and Dempsey announced the decision, President Barack Obama issued a statement of support.

"Our armed forces have taken another historic step toward harnessing the talents and skills of all our citizens," he said. "Today, every American can be proud that our military will grow even stronger with our mothers, wives, sisters and daughters playing a greater role in protecting this country we love."

Obama has nominated former Sen. Chuck Hagel, a Republican, to succeed Panetta as defense secretary.

The decision to lift the combat exclusion for women was not welcomed in all corners.

"The people making this decision are doing so as part of another social experiment, and they have never lived nor fought with an infantry or special forces unit," said retired Lt. Gen. Jerry Boykin, a former commander of Delta Force.

Such units, he said, must endure sustained operations for extended periods in primal living conditions with "no privacy for personal hygiene or normal functions." The decision to integrate the genders in such units, he said, "places additional and unnecessary burdens on leaders at all levels."

First Lt. Gregg Zavadsky of the Maryland National Guard said he trusted that commanders had thought through the decision and concluded that it was in the best interest of the military.

"It's going to be a change," he said. "But soldiers are trained to adapt to any situation. I don't think it's going to be an issue.

"I know a lot of women who are capable of serving in these combat arms positions."

Kupcho, stymied in her ambition to drive tanks in combat, said she is satisfied with her career as a public affairs officer for the Maryland Guard, a role that took her to Afghanistan in 2011 and 2012.

While she no longer harbors dreams of joining an armored unit, she applauded the decision that would make it possible.

"It's a great opportunity for women who want to pursue these jobs," she said. "It's going to level the playing field."

By the time Barbara Mikulski ran for Congress in 1976, you could see the scorched earth of the battles she and others had fought against a federal highway plan that would have turned downtown Baltimore and some of its best neighborhoods into an ugly savannah of concrete.